Question: 4 binders cost $5.92. Which equation would help determine the cost of 12 binders?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 4 binders. We want to know the cost of 12 binders. We can write the numbers of binders as a proportion: $\dfrac{4}{12}$ We know 4 binders costs $5.92. We can let $x$ represent the unknown cost of 12 binders. The proportion of these costs can be expressed as: $\dfrac{\$5.92}{x}$ The cost changes along with the number of binders purchased, and so the two proportions are equivalent. $\dfrac{4}{12} = \dfrac{\$5.92}{x}$